Field of the Invention
The aspect of the embodiments relates to a recording-element substrate that is to be mounted on a liquid discharge head, a recording head, and a recording apparatus.
Description of the Related Art
An example of an information-output apparatus that records information regarding a desired letter, image, or the like onto a recording medium, such as a sheet or a film, is a recording apparatus that performs recording by discharging a liquid. The recording apparatus performs recording by causing liquid droplets discharged from a liquid discharge head to land on a recording medium. There are various methods by which such a liquid discharge head discharges a liquid. A thermal method is a well-known example of a liquid discharging method. The thermal method is a liquid discharging method in which liquid droplets are discharged by using foaming of a liquid such as an ink that is induced by thermal energy generated by passing a current through a heater, which is brought into contact with the liquid, for about a few μs. In general, a liquid discharge head that is used in the thermal method is provided with a recording-element substrate that includes a heater (hereinafter also referred to as heating element), which serves as a recording element.
The recording-element substrate includes a substrate on which the heater has been formed, a flow-path-forming member, and a discharge-port-forming member. An example of the configuration of the heater is one in which a portion of a heater electrode provided on the substrate is removed, and a heater layer positioned between portions of the heater electrode functions as the heater. The heater is coated with a cavitation resistant layer that protects the heater against heat and physical and chemical impacts generated at the time of foaming and defoaming of a liquid. In addition, an insulating layer is disposed between the heater and the heater electrode and the cavitation resistant layer.
An example of a process for manufacturing a liquid discharge head will now be described. First, a heater and the like are formed on a substrate in a wafer state, after which a dry film is attached to the substrate. Then, a flow-path-forming member and a discharge-port-forming member are formed by using a resist coating or the like. Next, the substrate in a wafer state is attached to a dicing tape and cut by using a diamond saw or the like. The recording-element substrate that has been cut into individual substrates is cleaned in order to remove swarf and the like while being attached to the dicing tape. After that, the recording-element substrate is separated from the dicing tape, and each of the individual substrates is incorporated into a liquid discharge head.
Issues may sometimes occur in a recording-element substrate due to electrostatic discharge (hereinafter referred to as ESD) during, for example, the above-described process for manufacturing a recording-element substrate and during a recording operation performed by a liquid discharge head. U.S. Pat. No. 7,267,430 describes a phenomenon in which, in a recording-element substrate that includes an insulating layer having a film thickness of about 200 nm, electrical breakdown occurs in the insulating layer, which is positioned between a cavitation resistant layer and a heater electrode, due to ESD. In addition, U.S. Pat. No. 7,267,430 describes a configuration in which the cavitation resistant layer is connected to a grounded-gate metal oxide semiconductor (MOS) in order to prevent the phenomenon from occurring. Furthermore, U.S. Pat. No. 7,267,430 describes an advantageous effect in which, by employing the above configuration, a current that has been generated by ESD and that has flowed in the cavitation resistant layer can escape to a substrate, and thus, electrical breakdown can be prevented from occurring in the insulating layer positioned between the cavitation resistant layer and the heater electrode.